The present invention relates to an aqueous composition for plasticising or softening paint, varnish and similar coatings (e.g. lacquers) prior to stripping the coating from a surface.
Solvent-based compositions are known, for plasticising or softening paint, varnish and similar coatings prior to stripping. The composition is applied to the coating, for example by brush application, is then left for a period of time to allow the composition to plasticise or soften the coating to a desired extent, and then the stripping operation is carried out mechanically. Such compositions, and the fumes they emit, are generally irritant, smelly and toxic. This necessitates special storage and handling procedures, particularly for commercial use, as well as protective clothing and equipment for users. Moreover, the compositions are liquid at room temperatures, which means that it is difficult for them to work effectively on vertical surfaces.
Efforts have been made to provide aqueous compositions having effective softening and degrading actions, which could replace solvent-based systems.
DE-A-3438399 (Example 1) describes such an aqueous composition, containing a total of 66% by weight dibasic acid esters (dimethyl succinate, dimethyl glutarate and dimethyl adipate), 2% by weight of an organic thickening agent (cellulose acetobutyrate) and 5% by weight of water, together with additional ingredients such as surfactants. Such a composition is described as softening and moistening a paint coating after 2 hours, sufficiently for it to be completely removed by steam jet blasting, with the softening and moistening effect being retained for at least 24 hours after application.
EP-A-0294041 describes further aqueous compositions, containing up to about 50% by weight dibasic acid esters, small amounts of thickening agents (clay/cellulose mixtures) and at least about 50% by weight water, together with additional ingredients such as surf actants. Such compositions were tested in comparison with a methylene chloride paint stripper (Comparative Example A) and the known composition from DE-A-3438399 (Comparative Example B), for their ability to remove four layers of paint from a pine board. With the board horizontal (Table II), only the methylene chloride stripper removed all four layers, and only one of the eight tested compositions performed betterxe2x80x94and then only slightly betterxe2x80x94than the known composition from DE-A-3438399. The performance was found to be retained with the board in a vertical orientation.
However, the compositions of EP-A-0294041 do not provide a significant improvement in practical commercial terms. There is a tendency for the compositions to dry out and/or to separate out when left on the surface to be treated, so reducing their effectiveness. In addition, the compositions are not clear enough to be able to see the coating after the composition has been applied, so that it can be difficult to judge when the softening action has proceeded sufficiently.
EP-A-0407952 describes viscous, pasty or gel-like aqueous compositions, said to be improvements on the compositions of EP-A-0294041, in which the paint-softening xe2x80x9csolventsxe2x80x9d generally comprise 20 to 60% by weight of the composition, preferably 30 to 45%, the remainder of the composition being an aqueous solution of common surfactants with one or more common thickeners. Dibasic esters are generally indicated as possible xe2x80x9csolventsxe2x80x9d, although none is specifically mentioned. Laponite RD is exemplified (Examples G, H and I) as an example of a common thickener.
The compositions of EP-A-0407952 do not provide a significant improvement in practical commercial terms. The viscosity of the compositions is not particularly high, notwithstanding the rather low water content (about 50% by weight is exemplified). The compositions contain too much organic material, and too many individual organic components, to be feasible from either an environmental or commercial point of view.
EP-A-0648820 describes further aqueous compositions employing rather low levels of water and high levels of active and carrier organics dispersed in the water by means of surfactants. As potential surfactants there are generally mentioned alkylene-oxide (ethylene oxide or propylene oxide)-added type nonionic surface active agents.
The known aqueous compositions overcome some of the disadvantages of the former solvent-based compositions, but there nevertheless remains a need for improved or at least alternative aqueous plasticising or softening compositions.
More particularly, there remains a need for an aqueous composition which can work at least as well as known methylene chloride strippers, and in which water forms the major portion of the composition.